Effects of cataract type and location on visual function: The Blue Mountains Eye Study

Purpose. To measure the effect of cataract type, severity and location on presenting, and best-corrected visual acuity, contrast sensitivity, and glare disability. Methods. In all, 3654 (82.4% participation rate) eligible noninstitutionalised residents aged 49 years or older, living in two postcode areas of the Blue Mountains, Australia, received detailed eye examinations including visual acuity, contrast sensitivity, and glare disability testing. Data from right eyes were analysed using multiple regression modelling. Results. The effect of age on visual acuity and contrast sensitivity only became evident in persons aged at least 60 years. Cataract severity was inversely related to visual acuity and contrast sensitivity. Late posterior subcapsular cataract caused the greatest reduction in visual acuity. Early grade cataract caused significant reduction in contrast sensitivity at intermediate and high spatial frequencies, but late grade cataract reduced contrast sensitivity across all spatial frequencies. There was insufficient study power to detect consistent significant effect of cataract on glare disability tests or cortical cataract location on visual function. Conclusions. Age at least 60 years, cataract type, and cataract severity were principal determinants of visual acuity and contrast sensitivity in this study. Axial and superotemporally located cortical cataract had the greatest effect on visual function tests.